1. Field of the Invention
This invention relates to a thin film transistor substrate applied to a display device, and more particularly to a thin film transistor substrate and a fabricating method thereof that is adaptive for simplifying the fabrication process. Also, the present invention is directed to a liquid crystal display panel employing the thin film transistor substrate and a fabricating method thereof that is adaptive for simplifying the fabrication process.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) controls the light transmittance of a liquid crystal having a dielectric anisotropy using an electric field to thereby display a picture. To this end, the LCD includes a liquid crystal display panel for displaying a picture using a liquid crystal cell matrix and a driving circuit to drive the liquid crystal display panel.
Referring to FIG. 1, a related art liquid crystal display panel includes a color filter substrate 10 and a thin film transistor substrate 20 that are joined to each other having a liquid crystal 24 therebetween.
The color filter substrate 10 includes a black matrix 4, a color filter 6 and a common electrode 8 that are sequentially provided on an upper glass substrate 2. The black matrix 4 is provided in a matrix on the upper glass substrate 2. The black matrix 4 divides an area of the upper glass substrate 2 into a plurality of cell areas containing the color filters 6 and prevents light interference between adjacent cells and external light reflections. The color filters 6 are placed in the cell area defined by the black matrix 4, with adjacent cells alternating between red(R), green(G) and blue(B) filters, thereby transmitting red, green and blue light. The common electrode 8 is formed from a transparent conductive layer entirely coated onto the color filter 6, and supplies a common voltage Vcom that serves as a reference voltage for driving of the liquid crystal 24. Further, an over-coat layer (not shown) to smooth the color filter 6 may be provided between the color filter 6 and the common electrode 8.
The thin film transistor substrate 20 includes a thin film transistor 18 and a pixel electrode 22 provided for each cell defined by a gate line 14 crossing a data line 16 on a lower glass substrate 12. The thin film transistor 18 applies a data signal from the data line 16 to the pixel electrode 22 in response to a gate signal from the gate line 14. The pixel electrode 22 formed from a transparent conductive layer supplies a data signal from the thin film transistor 18 to drive the liquid crystal 24.
The liquid crystal 24 having a dielectric anisotropy is rotated by an electric field formed by a data signal on the pixel electrode 22 and a common voltage Vcom on the common electrode 8 to control the light transmittance of the liquid crystal 24, thereby implementing a gray scale level.
Further, the liquid crystal display panel may include a spacer (not shown) to fix a cell gap between the color filter substrate 10 and the thin film transistor substrate 20.
In the liquid crystal display panel, the color filter substrate 10, and the thin film transistor substrate 20 are formed by a plurality of mask processes. One mask process includes a number of processes such as thin film deposition (coating), cleaning, photolithography, etching, photo-resist stripping and inspection processes, etc.
Because the fabrication of the thin film transistor substrate includes semiconductor fabricated processes and requires a plurality of mask processes, the manufacturing cost the liquid crystal display panel increases because of the complexity of the manufacturing processes. Therefore, the thin film transistor substrate of the present invention has been developed to reduce the number of mask processes.